Television and the like



' June 13, 1933. WALTON 3 914 3114 TELEVISION AND THE LIKE Filed March 16 1932 Patented June 13, 1933 UNITED STATES GEORGE WILLIAM WALTON, OF LONDON, ENGLAND 1' TELEVISION AND THE LIKE Application filed March 16, 1932, Serial No. 599,272, and in Great Britain February 20, 1931.

The present invention relates to television and the like systems, and is particularly, although not exclusively concerned with methods and means for scanning one-dimensional 5 images of an object which are of the type described in the specifications of Patent applications Serial Nos. 400,883 and 426,344.

Throughout this specification'the word object will be used to designate any type of moving or stationary picture, scene, view or the like.

It has already been proposed to scan an ordinary two-dimensional object, or an image thereof, in a plurality of zones, impulses being transmitted by either one channel or by separate channels equal in number to the number of zones scanned. If one channel be used, the first lines of all the zones are scanned successively, then the second lines successively, then the third, and so on for the whole image. If more than one channel be used the separate zones may be scanned simultaneousl The object of the first of these known methods is to break up trains of frequencies in the electrical impulses, and the object of the second method is to reduce the frequency with which the picture must be scanned.

It is an object of the present invention to provide means whereby one-dimensional images may be transmitted over a plurality of channels.

It is a further object of this invention to provide a television or the like system, applicable to one or two-dimensional image transmission, in which diflerent zones of the image are transmitted simultaneously over different channels and in which at least one of the channels serves to transmit all the zones of the image. Preferably each channel serves to transmit all the zones in turn in which case the lines of demarkation between zones which have usually been visible in thereproduced image in known multi-channel systems are avoided.

Itis well known that scanning apparatus used at the transmitting station of a television system may be used, in an inverse manner, at the receiving station of that system. Sufficient descriptions of apparatus used at the transmitting station will be described herein to enable a person skilled in the art to construct the receiving apparatus.

The in'vention will now be described, by way of example, with reference to the accompanying drawing, in which:

Fig. 1 illustrates, in perspective, an optical system for producing one-dimensional images of the kind described in specifications Serial Nos. 400,883, and 426,344.

Fig. 2 illustrates the type of one-dimenslonal images formed by means of the system of Fig. 1.

Fig. 3 illustrates diagrammatically a form of echelon device which may be used accordmg to a feature of the present invention.

Fig. 4 illustrates the images formed with the echelon device of Fig. 3.

Figs. 5, 6 and 7 illustrate diagrammatically alternative Zone scanning arrangements in 7 accordance with the present invention, and

Fig. 8 illustrates a slit which may be used in any of the arrangements illustrated in Figs. 5, 6 or 7.

As described in the patent specifications 7 already referred to above, by means of the optical system of Fig. 1, a one-dimensional image of the object 1 can be produced at 7. The formation of this image is shown diagrammatically in Fig. 2.

In a method of scanning described in these earlier specifications, the one-dimensional image 7, or an image thereof, is swept by means, for example, of an oscillating mirror, over an apertured photo-electric cell. Since the images have definition only in their length it is suiiicient to move the images over the cell only in the direction of their length.

Since the images 7 have no definition in the direction of their width, the width of image scanned is immaterial, and therefore in the known method only that portion lying between the lines 21 and 22 of Fig. 2 is scanned.

In place of the echelon device of Fig. 1, which produces a regular one-dimensional image as shown in Fig. 2, there may be used an echelon device arranged as shown diagrammatically in Fig. 3, which produces an irregular one-dimensional image in which 1 lines which are spaced from each other in the 0 ject, are, in the one-dimensional image thereof, so arranged that they can be scanned successively.

The arrangement of the lines of the onedimensional image produced by means of this echelon device is shown in Fig. 4. The image lines 8a, 9a, 10a corresponding to the lines 8, 9, 10 of the object 1 0 Fig. 1, which are adjacent in the object, are, in the one-dimensional image arranged other than adjacent.

The one-dimensional image of Figures 3 or 4 can be scanned according to this invention in a variety of ways, some of which will be described later, by sweeping an image thereof over a plurality of apertured photoelectric cells, and the order in which lines are scanned by any one aperture is then 8a, 11a, 14a, 17a, 90, 12a, 15a, 18a, 10a, 13a, 16a, 190:. By suitably arrangin the laminations of the echelon device of Fig. 3, the lines of the image may be scanned in any desired-order. Since the representations of the lines of the two dimensional object 1 have in Fig. 4 been displaced so that they do not overlap one another, there is no restriction (other than that of practical convenience) upon the widths of the line representations in Fig. 4. If each line is regarded as composed of a row of elemental areas, each may be represented by a strip perpendicular to the row and of any desired length, for example extending from top to bottom of the figure.

In Fig. 5 there is illustrated a methodof scanning the one-dimensional ima es 7 which may be produced with the aid 0 either the echelon device 6 of Fig. 1, or of that illustrated in Fig. 3. A secondary image 23 of the images 7 is formed by means of an osclllatory mirror 24, in the plane of an opaque screen 25. The mirror 24 is placed in such a position, and its amplitude of swing is such, that the image 23 is oscillated between the two extreme positions indicated by the full line 23 and the dotted line 26. In order that light rays from the one-dimensional ima e 7 shall be equally operative, a field lens 51101 shown), which may be spherical or cylindrical, is placed before the image 7 and has a focal length equal to the distance of the oscillating IIllIIOl 24 from this lens so that the whole of the light from the image 7 is concentrated on to the oscillating mirror. Light from the image 7 reflected by the mirror 24, is thrown on to four equally spaced slits 27, 28, 29, 30, behind each of which is placed a photoelectric cell, and in order that the slit shall not be too small a lens system may be interposed between the mirror and the slit for the purpose of enlarging the image thrown on to the slit. The length of the slit (i. e. the dimension perpendicular to the paper in Fig. 5) and the width of the stixograph in the same direction, are such that, by sweeping the stixograph image in a straight line direction, the whole of the stixograph is caused to aifect the cell 30. This arrangement is not the preferred one, since the cells 27, 28 and 29 do not sweep over the whole image.

In a modification, the oscillating mirror 24 has a swing which covers only one section of the one-dimensional image instead of a swing which embraces the whole of the line picture. If the one-dimensional image is divided into four sections, then the oscillating mirror is given a maximum swing which will cover a quarter of the length of the image, and the four fixed scanning slits are so disposed that when the oscillating mirror is at rest the centre point of each section of the image is thrown on to one of the slits, and so one slit corresponds to one section of the image. The image 7 is thus scanned in four zones simultaneously, each zone being dealt with by its own photo-electric cell which con stitutes the beginning of a separate transmission channel. In this arrangement none of the cells scan the whole image and each deals only with its own zone thereof.

A similar multiple scanning arrangement would be used in an inverse manner at the receiver, in which, of course, a source of light modulated by a corresponding picture current will be placed behind each of the fixed slits, or will have an individual light modulating device and one or more sources of light.

A third scanning arrangement in accordance with the present invention in which each channel serves to transmit the whole image is illustrated in Fig. 6. An image 23 of the one-dimensional image 7 is, as before, thrown on to a screen 25 by means of an oscillating mirror 24. The amplitude of swing of the mirror is such that the image 23 moves be- In tween the positions 23 and 26. In the screen 25 are six equally spaced slits 31, 32, 33, 34, 35, 36 behind which are photo-electric cells 37a, 38a, 39a, 37b, 38b and 39b. The distance between corresponding a and b slits is equal to the length of the image 23, and the cells 37a and 37 b are connected in parallel, as also are the cells 38a, 38b, and 39a, 39?).

As the mirror 24 oscillates three points in the image 23 are scanned simultaneously, and

each pair of cells scans the whole image. In this arrangement one scanning aperture, for example 38a, becomes operative on the image before the preceding one, for example 37a has finished scanning the whole image, so that three apertures are always operative at the same time on the image. Thus each pair of connected cells and each channel deals with the whole image. Pairs of slits are used because as the mirror swings, each slit becomes at some instant inoperative on the image, but immediately it does so, the other slit of the pair becomes operative. The advantage of this method is that there is no possibility of a received picture appearing in definite sections which may possibly overlap or be disjointed, but that the whole appears as a properly connected picture. Each pair of slits may be provided with an individual colour filter or with a pair of photo cells having a selective response in a certain part of the visible spectrum, each pair having a difl'erent region of selective response.

When the scanning is unidirectional instead of oscillatory, for example when a mirror drum is used, the cells do not require to be connected in pairs. 7

At the receiver a similar arrangement is used in the inverse manner, light sources modulated in accordance with the received impulses replacing the photo-electric cells of the transmitter.

A modification of the last described scanning arrangement is illustrated in Fig. 7.

Here the extreme positions of the image 33' are arranged to be at 33 and 26, and it will be seen that in this case the cell 40 scans the whole of the image, therefore the number of cells necessary is one less than in the case of Fig. 6. Otherwise the arrangements of Fig. 6 and 7 are exactly similar.

Those multiple scanning arrangements according to Figures 6 and 7 in which each aperture scans the whole of the image may be used according to the present invention whether the image be one or two dimensional, but in the case of a two-dimensional image means must, of course, be provided for moving the image 23 or 33 in a direction perpendicular to the plane of Figs. 6 and 7 whilst also moving it in that plane, (for in- Stance, a mirror drum).

In all of-the methods of scanning so far described it a one-dimensional image is to be scanned, the latter, or an image thereof,

7 is swept over a light-sensitive device in front of which there is a slit. Now as in the onedimensional image there is no definition in one direction, the image may be arranged on the slit so that there is no definition in the direction of the length of the slit. Such an arrangement is illustrated in Fig. 8, 41 indicating a part of the one dimensional image, and 42 the slit. By placing behind the slit three apertures 43, 44, 45, the light from each of them will be divided into a corresponding number of sections, and each of these apertures may be provided with a diiferent coloured filter, or the photo cell behind each aperture, and individual to that aperture, may be such as to have a selective response in a certain part of the visible spectrum, and the photo cells appertaining to different slits have selective responses in different parts of the spectrum. The electric currents from each photo cell are, of course, transmitted along a separate channel and are applied to an individual light modulation device in the receiver. At the receiver a very similar scanning arrangement is used but in an inverse manner; if three colours are used at the transmitter then there are three light modulating devices, which may or may not have individual sources of light. Here each cell and each channel serves to transmit the whole of the object. The cells do not traverse the same paths on the stixograph but as they are spaced apart in the direction of no definition on the stixograph the image transmitted by one cell is equivalent in all respects to that transmitted by the other cells.

To those skilled in the art there will be apparent many modifications, other than. those described above, lying within the scope of the present invention as definedin the I appended claims. For example, the echelon device forming the one-dimensional images may be such as to pick out the lines of the object in any desired manner not necessarily in that order described herein; the other may be, for purposes of secrecy, quite irregular, and there are obviously many combinations of different kinds of echelon devices with the dilferent methods of scanning described herein.

Clearly, in all cases, the image to be scanned may remain stationary and the aper-' ture moved, usually with its co-operating light sensitive device.

I" claim:

1. Television and the like transmitting apparatus comprising optical means adapted to produce simultaneously from an object an image in which adjacent lines of the object are longitudinally displaced relatively to one another, a plurality of scanning apertures spaced apart in the direction of said longitudinal displacement and means for producing relative motion substantially in said direction between said image and said apertures.

2. Television and the like apparatus comprising optical means adapted to produce simultaneously from an object, an image in which adjacent lines of the object are longitudinally displaced relatively to one another, a plurality of electro-optical means spaced apart in the direction of said longitudinal displacement, and means for producing relative motion substantially in said direction between said image and said means.

3. Television and the like apparatus comprising a plurality of transmission channels, a plurality of spaced scanning means each adapted to co-operate with one of said channels, means for producing in the neighborhood of said scanning means an optical image of an object to be transmitted and means for producing relative motion between said image and said scanning means solely in the direction of said spacing, each of said scanning means being thus adapted to sweep over successively and scan the same part of the image.

4. Television and the like receiving appa ratus adapted to co-operate with a plurality of transmission channels and comprising means for producing a plurality of spaced light beams each adapted to co-operate with one-of said channels, a reproducing surface and means for producing relative motion between each of said beams and said surface solely in the direction of said spacing, each of said beams being adapted to sweep over successively the same part of said surface and to reconstitute the whole of the image to be reproduced and only one of said beams bein Y at any time operative on one line of sai image.

5. Television and the like receiving apparatus adapted to co-operate with a plurality of transmission channels and comprising means for producing a plurality of pairs of spaced light beams each pair being adapted to co-operate with one of said channels, a reproducing surface and means for producing relative motion between each of said beams and said surface solely in the direction of said spacing, each of said pairs of beams being adapted to reconstitute the whole of the image to be reproduced.

6. Television and the like receiving apparatus comprising a reproducing screen, optical means adapted to produce upon said screen simultaneously from an image in which adjacent lines of an object are longitudinally displaced relatively to one another an ordinary two dimensional image of said object, a plurality of light sources spaced apart in the direction of said longitudinal displacement, a housing for said light sources, said housing having apertures therein corresponding to said light sources, means for producing images of said apertures in the neighborhood of said optical means and means for producing relative motion between the last mentioned images and said optical means.

7. Television apparatus according to claim (3 wherein at least one of said apertures has associated therewith a plurality of light sources the color of one of said sources being different from the color of another of said sources.

8. Television apparatus according to claim 6, wherein at least one of said apertures has associated therewith a plurality of light sources, each of said sources bein associated with a color filter and the color 0 one of said filters being different from the color of another of sald filters.

9. Television and the like transmitting apparatus comprising optical means adapted to produce simultaneously from an object an image in which adjacent lines of the object are longitudinally displaced relatively to one another, a plurality of scanning means spaced apart in the direction of said longitudinal displacement, means for producing relative motion substantially in said direction between said image and said scanning means, a plurality of light-sensitive devices name to this s cification.

G-EOR E WILLIAM WALTON. 

